In the cited patent application of Hiram Hart, a method is described for the quantitative determination of a biological-material in a fluid, particularly the amount of antibodies or antigens present in a immunological fluid under assay. To obtain the degree of sensitivity and accuracy desired, it had been found necessary, for some instances, to utilize reagents of relative freshness. For instance, when the reagents were prepared well in advance of the actual use in the cited quantitative procedure, it was found that in some cases, the magnitude of the assay signal was reduced. This was compounded by a significant background signal arising from fluorescence of the polystyrene of which the tritiated particles are composed. Needless to say, these effects in some cases, mask or interfere with the response desired, i.e.; a detectable light-signal which could be correlative to the amount of biological-material present in the fluid under assay. Clearly, with both these inherent difficulties present, the accuracy and sensitivity of the process were placed in jeopardy. To be sure, however, when the reagents were immediately prepared, prior to use, the accuracy and sensitivity of the cited method was maintained at a very high and acceptable level. Again, however, if a substantial length of time had expired between preparation and use, the utility of the method was placed, in some instances, in issue.
For instance, when the scintillating latex-particulates were used in the quantitative method described in the cited patent application of Hiram Hart, it was found that the supernatant of an aqueous suspension which had been standing at room temperature, for several days, was often slightly opalescent. The particles themselves had become less effective scintillators. As a result of this temperature dependent effect which is attributed to a gradual leaching of scintillant from the particles and into the medium, the accuracy and sensitivity of the analytical method as a routine laboratory procedure was placed in issue. Another difficulty, which compounded the problem, found basis in the inherent background signal of the tritiated-latex-particulates themselves. Again, in specific instances, the general utility of the process was questioned because the background signals interfered with the sensitivity and accuracy of the responsive signal in the quantitative determinative method described.
It was found, however, that the inherent properties and functions of the energy-emitting latex-particulates, which were desired, could be maintained, or highly improved, by the specific procedures of preparing them. These energy-emitting latex-particulates include both the tritiated-latex-particulates and the scintillating-latex-particulates. Both were prepared to enhance their use in the cited quantitative procedure. As a result, the signal desired was clearly defined, responsive to activation, and quatitatively correlative to the presence in the fluid of an exact amount of biological-material under assay, and these features were readily obtained by methods of preparing the particulates themselves. The effects were accomplished by the elimination of the background masking of the desired responsive signal which occurred with the production of opalescence and significant background signals both of which were inherent in the use of some of the particulates themselves.
It is therefore an object of this invention to provide energy-emitting latex-particulates which do not exhibit masking effects on the quantitative signal, whether physical or chemical when used in the non-destructive method of assay of biological materials, particularly the assay of immunological materials such as antibodies and antigens.
A further object of the invention is to provide scintillant latex particulates having inherent stability, and a greatly extended life when in the fluid suspension state.
Another object of this invention is to provide improved tritiated latex particulates with the responsive signal indicating the quantity of immunological material in the fluid under assay.